Nonvolatile semiconductor memories generally retain stored data even when not powered. Transistor-based nonvolatile memories, such as flash memory and electrically erasable programmable read-only memory (EEPROM), offer fast read access times and shock resistance making them desirable in various applications. Some applications of nonvolatile memories include data storage on computing devices, mobile phones, portable audio players, and other consumer electronic products.
FIG. 1 illustrates a circuit diagram of an example transistor-based nonvolatile memory array 100. Transistor-based nonvolatile memory array 100 includes a plurality of transistor-based nonvolatile memory cells 110. Each transistor-based nonvolatile memory cell 110 is associated with a word line (e.g., WL0 through WLn) and a bit line (e.g., BL0 through BLm). Transistor-based nonvolatile memory array 100 may be formed by nonvolatile memories that store data using one or more transistors as a storage element. Transistor-based nonvolatile memories include programmable read-only memory (PROM), electrically programmable read-only memory (EPROM), EEPROM memory, flash memory, or eFUSE memory.
As shown in FIG. 1, when transistor-based nonvolatile memory array 100 is implemented using EPROM, EEPROM, or flash memory, each transistor-based nonvolatile memory cell 110 includes a floating-gate metal-oxide semiconductor field-effect transistor (MOSFET). The floating-gate MOSFET (FGMOS) can store charge in an electrically isolated floating gate. The electrical isolation allows the floating gate to retain a charge for extended periods of time without power. A fully charged floating gate may represent a logical “0” state and an uncharged floating gate may represent a logical “1” state, or vice-versa.
Emerging nonvolatile memory technologies are being developed to address various limitations associated with transistor-based nonvolatile memories such as flash memory. For example, most commercially available flash memories suffer from relatively low write endurance. A typical flash memory may be capable of enduring up to 1×105 write cycles (also referred to as program/erase cycles); whereas some emerging nonvolatile memories, such as magnetic random access memory (MRAM), may be capable of enduring up to 1×1012 write cycles. As another example, flash memory arrays may suffer from scaling issues such as read disturb (sequential read cycles that cause nearby cells to change over time) and reductions in write endurance.
Emerging nonvolatile memories, however, have shortcomings. For example, high operating temperatures may cause data errors such as flipped bits in some emerging nonvolatile memories such as resistive nonvolatile memories. Such data errors may lead to system crashes, data corruption, and/or security vulnerabilities. Moreover, subjecting emerging nonvolatile memories to high manufacturing and storage temperatures may cause data retention issues such as systematic data drift, data loss, significant data corruption, and decreased data retention times.